40+ 12Ax7 Tube Preamp Schematic Background. I used 12au7 tubes and a b+ voltage of about 150v. From the 12ax7's average plate characteristics graph below, i have the gain of the preamp is 51.

12AX7 Tube (valve) Preamplifier Kit
12AX7 Tube (valve) Preamplifier Kit from diyaudioprojects.com
Each tube sample was again tested in the same preamp circuit and an oscilloscope was connected to the amplifier output to monitor the amplitude of the voltage spike produced by tapping on the tube's glass envelope. Acoustic, ampeg, boogie, carvin, crate, danelectro, dumble the vacuum tube is, without question, an ancient electrical component. The schematic of the preamplifier section is shown in figure 01.

This is as close as i can get to the original schematic diagram of the tube/valve guitar preamp i built six years ago.

(please note that this circuit is © silicon chip online and permission to host the. 12au7 tube preamplifier has been slightly modified so that i could use parts i had on hand. The first design consideration is the tube's idle current and plate voltage. Many tube bass/guitar preamps are actually hybrid preamps that use one tube, often a 12ax7 with other semiconductor/transistor circuits.